Two forehands
You don't play two forehands for returns. Switching hands is troublesome. And it's not worth the extra headache.

Two backhands
It's just called a two handed forehand. This is better than two forehands but suffers from the lack of reach that comes with being two handed. But some people feel damn comfortable with it so leave them be.

Playing lefty
There is no downside. Look at Nadal's career. Now look at your student. Back to Nadal. Sadly, your student is not Nadal. However, if you teach him to play lefty instead of some other gimmicky stuff, he could someday win a professional tournament.